Mental health courts are one of most rapidly and widely disseminated jail diversion strategies for persons with severe mental illness; however, little is known about how mental health courts engage participants in services and poor mental health outcomes have been linked to substance use and poor service engagement (Gains Center, 2010). Mental health courts must include clinical interventions to improve engagement and address substance use. A promising intervention for mental health courts is dual diagnosis motivational interviewing (DDMI) (Martino, Carroll et al., 2002); however, to date, there have been no randomized clinical trials of DDMI in mental health court settings (GAINS Center, 2010; Morrissey et al., 2009). This R34 application responds to RFA-MH-11-061, Improving Evidence-Based Mental Health Screening and Treatment for Persons with Mental Disorders in the Justice System, and proposes to conduct a feasibility study of a small-scale randomized clinical trial of DDMI in a local mental health court. Our long-term goal is to secure R01 funding to conduct a multi-site, randomized clinical trial to demonstrate the effectiveness of DDMI in mental health court settings. We will pursue the following two specific aims: (1) Assess the feasibility of implementing a randomized clinical trial of DDMI in a local mental health court (primary aim); and (2) Determine the impact of DDMI on behavioral health and criminal justice outcomes for persons with severe mental illness who participate in mental health court (secondary aim). Once feasibility has been established, we will analyze the collected data within an intent-to-treat experimental design with 90 mental health court participants randomly assigned to two conditions (DDMI vs. treatment as usual) with outcome assessments occurring at 3-, 6- and 9- months. Our hypothesis is: mental health court participants who receive DDMI will have better treatment engagement and compliance than participants who receive treatment as usual. Our expected outcomes include: (1) a clear demonstration of the feasibility of implementing DDMI in a mental health court, (2) clear evidence that randomized clinical trials can be implemented successfully in mental health court settings, and (3) presumptive evidence that DDMI improves outcomes for mental health court participants. This proposal is well-aligned with the mission and strategic objectives of the NIMH and our findings will enable us - and other investigators - to undertake larger-scale, multi-site randomized clinical trials to establish the effectiveness of DDMI in mental health court and other court settings. With over 280 mental health courts in the U.S., the integration of DDMI within these settings will also provide a new context for addressing substance use for the many thousands of justice-involved persons with severe mental illness, further enhancing the broad public health and public safety significance of our research agenda.